In the News (Tue 20 Nov 18)

176) is based, in part, on UK government-sponsored impacts analyses (1, 2) that estimate that by the 2080s, because "of continued warming, millions more people around the world may in future be exposed to the risk of hunger, drought, flooding, and debilitating diseases such as malaria.

For instance, the population at risk of malaria (PAR-M) in the absence of climate change is projected to double between 1990 and the 2080s, to 8,820 million (2).

Thus, it would be far more beneficial, and cost-effective, at least for the next several decades, to reduce vulnerabilities to current problems, especially if they might be exacerbated by climate change (e.g., hunger, malaria, drought, and flooding) (3).

The mean increases in annual precipitation from the 2020s to the 2080s for the Scotland and Scottish Borders land grid boxes are 6-16% and 6-14% respectively.

C of global warming (implying that by the 2080s the 2-year return period daily storm in the west of Scotland could increase from 40mm to around 60mm).

This pattern is consistent for all scenarios thorough to the 2080s where it becomes more clearly developed in the Medium-high and High scenarios with annual runoff in eastern Scotland predicted to rise by >20%.

Thus the scenarios for the 2020s are assumed to be representative of the period 2010-2039, the scenarios for the 2050s represent the period 2040-2069, and the scenarios for the 2080s represent 2070-2099.

By the 2080s lightning frequency may increase by up to 20 per cent, consistent with the anticipated increases in precipitation intensities.

Related to changing airflow patterns over the whole of the British Isles, for the 2080s period, analysis suggests a tendency for autumns to experience windier conditions, with a reduction in northerly and easterly airflows and an increase in southwesterly and westerly flow.

An area-averaged annual mean increase in precipitation of approximately 0.3% for the 2050s and 0.7% for the 2080s over the Pacific Ocean area is projected, either as a consequence of increases in atmospheric concentrations of GHGs or because of the combined influence of GHGs and sulfate aerosols.

An analysis of model-simulated daily temperature and precipitation data (from CSIRO and ECHAM model experiments) for the present-day atmosphere and for the two future time slices (2050s and 2080s) projects that the frequency of extreme temperatures during the summer is likely to be higher in all four regions.

Although it is difficult to obtain reliable regional projections of climate change from GCMs, some consistent patterns are beginning to emerge for the Pacific with regard to ENSO and precipitation variability.

By the 2080s, in a worst case scenario (in which sea level rises by nearly 3.6 feet for some NYC coasts), those areas that now would be inundated by a 100-year flood (that is, a flood with a recurrence interval = 100 years) instead could be flooded (on average) every four years.

That is, by the 2080s, a line that marks the floodwater limits for what is now a 100-year flood, would mark the limits of a four-year flood.

By the 2080s, in a worst case scenario, a '100-year flood' could inundate areas of NYC whose present elevation is less than 13.6 feet (10 feet due to storm surge plus 3.6 feet sea level rise).

However, by the 2080s the Medium-high and High scenarios are generating floods on the same rivers up to 20% to 30% larger than at present.

Since all river basins report an increase in the size of the 50 year flood, return periods for flows at that level are predicted to fall.

However, given the many limiting assumptions incorporated at many stages in the modeling exercise, the final values for t-year floods and the reductions in the return periods for what, at present, are 50 year floods should be regarded as no more than indicative.

Global sea-level rise was estimated from the thermal expansion calculated by the Hadley Centre climate model and ice melt contributions quoted in IPCC 1995 (IS92a scenario): the total rise by the 2080s is predicted to be 44 cm.

Presently the number of people at risk is approximately 10 million, rising to about 30 million in the 2080s under the reference scenario of constant (1990s) flood protection and no sea-level rise.

Most of the people at risk in the 2080s are concentrated in a few regions, particularly the southern Mediterranean, Africa, southern Asia and South East Asia (see the map at bottom opposite).

By the 2080s for the High Emissions scenario, parts of the southeast may be up to 5ºC warmer in summer.

Even for the Low Emissions scenario, by the 2080s about two summers in three may be as hot as, or hotter than, the exceptionally warm summer of 1995.

By the 2080s, sea level may be between 2 cm below (Low Emissions) and 58 cm (High Emissions) above the current level in western Scotland, but between 26 and 86 cm above the current level in southeast England.

As expected, the drying tendency increases with time, so is greater in the 2080s than the 2030s, and is larger under the scenarios which assume higher global temperatures (i.e., for 75% scaling than for 25% scaling).

For the most extreme scenario of Hadley 75% scaling, the average annual PED by the 2080s is 629mm at Lincoln and 693mm at Napier, suggesting an additional 6 weeks or more of reduced pasture growth in an average year.

The other two scenarios for the 2080s not given in Table 3.1 (ie, CSIRO 75% and Hadley 25%) are intermediate between the two scenarios shown.

By the 2080s the mid-IPCC scenario is for 1.5°C in Fiordland and 2.0°C in the northeast of the North Island.

However for 2080s annual mean rainfall, the regions of Taranaki, Manawatu-Wanganui, West Coast, inland Otago, and Southland tend to show increased rainfall for all scenarios, compared to Hawkes Bay and Gisborne which show rainfall decreases for all scenarios.

Under both the "low-medium" and the "medium-high" scenarios (which bracketed this 75% range), the drought risk was projected to increase in frequency during the coming century for all areas that are currently drought prone.

If the average precipitation trend from the past century were to continue over the next century (Current Trends Scenario), there would be an average of a 1% increase in precipitation by the 2020s, a 1.6% increase by the 2050s and a 2.3% increase by the 2080s.

The average annual precipitation forecasts from the HCGS scenario are: an 8.63% increase in the 2020s, a 10.37% increase in the 2050s and a 21.57% increase in the 2080s.

The precipitation levels for the 2050s would be a slight.13% higher than the average for the past 30 years, followed by a forecast of.07% increase in annual precipitation in the 2080s.

An area-averaged annual mean increase in precipitation of 3±1% in the 2020s, 7±2% in the 2050s, and 11±3% in the 2080s over the land regions of Asia is projected as a result of future increases in the atmospheric concentration of GHGs.

Under the combined influence of GHGs and sulfate aerosols, the projected increase in precipitation is limited to 2±1% in the decade2020s, 3±1% in the 2050s, and 7±3% in the 2080s.

Because much of tropical Asia is intrinsically linked with the annual monsoon cycle, a better understanding of the future behavior of the monsoon and its variability is warranted for economic planning, disaster mitigation, and development of adaptation strategies to cope with climate variability and climate change.

This means the current one-in-twenty year drought could occur (on average) between once every 5 years, and once every 10 years, in the 2080s under the 'low-medium' scenario (ie, 2 to 4 times more frequently than at present).

What is currently a 1-in-20 year drought is expected to become about a 1-in-10 to 1-in-5 year drought by the 2080s in Central Otago, northern and southern Canterbury, Marlborough, and the east cost of the North Island from Wairarapa to northern Hawke's Bay, southern Bay of Plenty and eastern areas of Northland.

The west coast of the South Island is expected to show no increase or a decrease in drought risk, and other western parts of the North Island show only a small to moderate increase in drought risk up to about a 1-in-15 year return period.

Research [15] shows that average annual temperatures across the UK may rise by between 2° and 3.5°C by the 2080s, with the degree of warming dependent on future levels of global greenhouse gas emissions.

In general there will be greater warming in the south and east than in the north and west of the UK (see Figure 2).

By the 2080s for the highest emissions scenario, parts of the southeast may be up to 5°C warmer in summer.

The datasets are differentiated by both their spatial resolution (square grid cells of either 50km or 5km) and by whether they consist of baseline or future climate information.

For selected climate variables, a 5km resolution set of model outputs has been created by interpolating the 50 km changes in climate generated by the model to match finer-scale variations in observed climate (a basic form of statistical downscaling).

They are presented as "climate scenarios" in for the same three time-slices (2020s, 2050s and 2080s) and refer to absolute values of projected future UK climate.

By the 2080s, sea level could climb by 24 cm to nearly 110 cm, in some locations (Figure 1).

The area at risk to flooding is commonly defined in terms of the 100-year flood (probability of occurring once in 100 years).

By the 2080s, the likelihood of a flood engulfing the area in blue (Figure 2) would be once in 50 years, given present rates of sea level rise, and as often as once every 4 years, in the worst-case scenario.

Mediterranean sea levels have fallen by as much as 20 mm relative to the Atlantic since 1960, probably as a result of declining freshwater input and consequent seawater density increase (Tsimplis and Baker, 2000).

Table 13-3: Estimates of flood exposure and incidence for Europe’s coasts in 1990 and the 2080s (new runs using model described by Nicholls et al., 1999).

The changes in flooding, shown in Table 13-3, indicate a significant increase in the incidence of coastal flooding by the 2080s, assuming no adaptation, particularly around the Mediterranean.

Carbon dioxide concentration at present is approximately 360 ppmv (parts per million by volume), and dependent on the emissions scenario which is adopted, is expected to increase to 498-697 ppmv by the 2080s.

The 2020s are considered to be representative of the period 2010-2039, the 2050s of 2040-2069 and the 2080s of 2070-2099.

Failure to appreciate this fact may result in impacts assessments attributing the effects on social or environmental indicators of both human-induced climate change and natural climate variability as if they were the effects of human-induced climate change alone.

In general, it is expected that the negative impacts of climate change on forests will have a greater impact than any positive effect due to an increase in growth rates as a result of elevated atmospheric carbon dioxide concentrations.

With unmitigated emissions of greenhouse gases, substantial dieback of tropical forests and tropical grasslands is predicted to occur by the 2080s, especially in northern South America and central southern Africa.

If emissions are reduced enabling atmospheric carbon dioxide concentrations to stabilise at 550 ppm (double the pre-industrial level), this loss would be substantially reduced, even by the 2230s.

C rise in temperature by the 2080s may seem small, and it is essential that the magnitude of these predictions is placed in context.

Over the last 50 years, the average summer temperature predicted for the Low scenario in the 2080s has not been approached, including the extreme years of 1976 and 1995.

Due to the high inter-annual variability in rainfall, predicted changes to winter rainfall are difficult to distinguish from natural variability, while for summer rainfall, a number of years (including 1976 and 1995) would fall into the ‘average’ category for the 2080s.

By the 2080s, London\rquote s summer extreme \par temperatures could be comparable with those of present-day New York.

Figures 2 and 3 show changes in average \par annual, winter and summer temperature, and changes in precipitation for the 2020s, \par 2050s and 2080s under the Low Emissions and High Emissions scenarios respectively.

\par \par Mean winter wind speeds may increase by as much as 10% by the 2080s, though this is very uncertain.}{\i\f34\fs16\cf18\lang1033\langfe1033\langnp1033 \par }{\i\f33\fs14\cf18\lang1033\langfe1033\langnp1033 \par }{\f32\fs16\cf18\lang1033\langfe1033\langnp1033 The number of storms each winter crossing the UK could increase from five (the 1961-90 average) \par to eight by the 2080s.